Question

The NSMutableArray can store every NSObject, but can I mention the NSMutableArray can get store my item only, for example, a NSMutableArray that store NSString only?
I remember that the java array can do that, can the objective C array do the similar things? Thanks.

Answer 1

Objective-C does not have this kind of generic constraint on NSArray/NSMutableArray. You have therefore two solutions:

• Subclass NSArray/NSMutableArray and check for element type. It is strongly discouraged as NSArray/NSMutableArray is a class “cluster” and not obvious to subclass.
• Create a category with specific methods that check the right type. You will have a compile-time enforcement of the type.